NOTE: I did flip a few pins in the list above! 18, 19, and 20 are GND, 21, 22, and 23 run 32 Volts. As for 24, I do not know, but it may be 32V as well. That pin only leads to the black cartridge.
I also found a few articles on “band gap voltage generation”, which is a method to generate a temperature independent voltage at precisely 1.25V. One of the pins looks like it is a reference for the 32V lines to keep the print quality perfect (stab in the dark 😉
Lastly, after reading many patents, there is likely an ID chip on the ink head that is read by the printer, as well as temperature sensors. So there are likely lines that transfer data from the head to the controller.